Difference between pressurized/dual line and single line outboard fuel tanks?

[Horsepoor]

I'm trying to find a replacement tank that was used on an old trailer to supply gas to a generator. The old tank (stolen from unlocked storage box) had a vent screw and 1 fuel line.

Looking on ebay for replacement tank to fit box, i've noticed there seem to be some tanks that don't show a vent screw on top of the tank cap, and some tanks that are advertised as "dual line" or "pressurized tanks." And some of the tanks that don't appear to have a vent screw aren't advertised as "pressurized" or "dual line." i've also seen ads for "pumps" that fit into some tanks.

Since all I ever had to do with the stolen outboard tank was open the vent screw on its cap, pump an inline priming bulb a few times to push gas the 15' or so to the generator area, I'm confused by the differences as I don't know the significance or purpose of "dual line" or "pressurized" or if one of those tanks could work for my purpose (I don't know what runs through the second line....or if being pressurized means it will interfere with the fuel pump work on the generator...etc.)

Any advice on what I should get/do?

Thanks in advance.

 

[nwcove]

Re: Difference between pressurized/dual line and single line outboard fuel tanks?

a "pressure" tank wont work for your purpose. replace with what was there. ( pressure tanks push gas via pressure from the engine, fuel pumps suck gas via a pulse from the engine. ie the old pressure tanks need to be sealed tight to work, and your missing vented tank needs to be vented to allow air in , so fuel can get out.

 

[Horsepoor]

Re: Difference between pressurized/dual line and single line outboard fuel tanks?

a "pressure" tank wont work for your purpose. replace with what was there. ( pressure tanks push gas via pressure from the engine, fuel pumps suck gas via a pulse from the engine. ie the old pressure tanks need to be sealed tight to work, and your missing vented tank needs to be vented to allow air in , so fuel can get out.

Somone on ebay says their tank is single line (can tell via the connector), but the cap doesn't have a vent screw on top. He doesn't know (nor do I) how such a tank is vented so a pump could draw fuel from it. Did OMC build in some little vent into the connector structure? Or is the cap gasket some kind of one way device, that lets air in but won't let fuel out?

 

[nwcove]

Re: Difference between pressurized/dual line and single line outboard fuel tanks?

i just bought an older omc steel tank, and it also has no vent screw, it appears to have two different positions for the cap....closed for transport and about an 1/8 turn open for vent. ( havent looked under the cap to see whats there to keep it from leaking for boating purposes tho)

 

[Horsepoor]

Re: Difference between pressurized/dual line and single line outboard fuel tanks?

i just bought an older omc steel tank, and it also has no vent screw, it appears to have two different positions for the cap....closed for transport and about an 1/8 turn open for vent. ( havent looked under the cap to see whats there to keep it from leaking for boating purposes tho)

Since I posted i called Evinrude Tech Dept to verify something I saw in another thread....in later tank models, they made the venting automatic through a hole and spring valve in the fuel connector housing assembly at the tank top...so it does vent and you didn't have to go through opening and closing the old screw type.

I don't know if the newer system presented any malfunction problems (clogging up?) that you would never have with the old screw type or gas cap opening....but it does save steps. . . and i think it avoids any fuel leaking out. MAYBE SOMEONE READING KNOWS THESE 2 ANSWERS?